1. Field of the Invention
This invention relates to a glass manufacturing apparatus and process and more especially to an apparatus and process in which an elongated locating member is employed for locating a molten metal body on the upper surface of an advancing ribbon of glass.
This apparatus and process are employed to impart predetermined characteristics to the upper surface of the ribbon of glass, usually, but not necessarily, float glass, by migration of an element or elements into the glass from a body of molten material which is held in contact with the upper surface of the advancing ribbon of glass by the molten body clinging to the underface of the locating member.
2. Description of the Prior Art
The migration of the element or elements into the glass from the molten body, which may be a molten metal or a molten alloy, is controlled for example by regulating the oxidising conditions at the interface between the glass and the body. More usually an electrolytic method is used in which the locating member acts as an electrode and is for example connected as an anode so that current is passed from the molten body through the glass, which is electrically conductive at the temperatures of operation in the float glass manufacture, to effect controlled migration of ions of an element or elements from the molten body into the upper surface of the glass.
It is found in practice that erosion of the undersurface of the locating member takes place, especially if the material of the locating member dissolves electrolytically in the molten body. Electrolytic solution of the locating member in the molten body may serve to replenish the molten body. Unfortunately, the erosion may also lead to uneven treatment of the glass. The front and rear faces of the lower part of the locating member, that is the upstream and downstream faces, considered with reference to the direction of advance of the ribbon of glass, especially the downstream rear face, are particularly susceptible to erosion and the erosion of the front and rear edges of the under-surface of the locating member causes the dimension of the molten body in the direction of advance of the glass to contract. This erosion, and hence the contraction, tends to vary across the width of the glass leading to uneven treatment of the glass. To maintain uniform treatment the locating member is replaced with consequent loss of production time and treated product.
It has been proposed to obviate this wear and maintain constant the length of the molten body considered in the direction of advance of the ribbon of glass for longer operating periods, by providing that at least the downstream edge of the locating member is formed of a material which is more resistant to wear by the molten body than the remainder of the locating member. This downstream edge portion of the locating member has taken the form of an insert keyed into the locating member.
It is a main object of the present invention to provide a different way of alleviating the problem of wear of the under face of the locating member by a control of the length of the molten body considered in the direction of advance of the ribbon to maintain that length uniform recognising that erosion of the underface of the locating member occurs and tends to be greatest at the upstream and downstream edges of the locating member.